A. Field of the Invention
The invention relates to signal processing and, more particularly, to digital processing of analog signals. The invention is especially useful in connection with frequency spectrum analyzers.
B. Prior Art
Signal processors in general transform an input signal of one kind into an output signal of another kind. In the past this processing had been done most generally in the analog domain, but in recent years has been increasingly performed in the digital domain. Because of the high speeds of such processing where frequency-translation operations are to be performed on the input data, it is necessary to filter the modulation products to extract only the desired side bands for subsequent processing. When only a narrow portion of the input band of the input data signal is to be analyzed, very narrow band filters are required and the filter design problem for either type of processing for (analog or digital) becomes severe.